The Apple Watch will have a battery-preserving “Power Reserve” mode, in which the device shows only the time, the New York Times reports, citing an unnamed Apple employee. Functions like “Power Reserve” don’t yet exist on any Apple products, such as iPhones, presumably because the battery-heavy functions—calling, Internet or GPS—are vital to the smartphone’s users.

Apple hasn’t announced the Apple Watch’s exact battery life, but CEO Tim Cook said in January that the watch will last “all day.”

More details about the Apple Watch will likely be unveiled during Apple’s March 9 event, ahead of the device’s release in April.

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